This invention relates to fast warm up cathodes and more particularly to fast warm up cathodes for use in cathode ray tubes.
In the past, many types of fast warm up cathodes have been proposed; however, most have not been commercially acceptable because of high failure rates or prohibited costs. To accomplish the same result many manufacturers of television receivers have adopted a so called "instant on" feature which provides heater current to all of the tubes in the receiver even if it is "off". While this system is very successful in accomplishing its purpose, it is very wasteful of electrical energy.
To rectify the energy waste, attention again turned to providing a fast warm up cathode; that is, a cathode which reaches operating temperature and provides a viewable picture on the screen of a cathode ray tube in the neighborhood of about 5 seconds. Such a cathode has recently been developed and is shown and described in U.S. patent application Ser. No. 409,041, now U.S. Pat. No. 3,881,124, assigned to the assignee of the present invention, the disclosure of which is here and incorporated by reference.
Such a cathode comprises basically a cup shaped cap having electron emissive material on the outer surface of the closed end thereof and a cathode stack which is attached to the cap by low heat conducting ribbons. A suitable heater is disposed within the cathode stack and cap. This structure works extremely well for its designed purpose but could be improved even further if the heat radiated from the heater could be conducted more readily and rapidly to the top cap of the cathode.